The present invention relates generally to the field of printing. More specifically, the present invention provides methods and apparatus for converting full color images into two-color images for printing at a two-color printer, for example a two-color thermal printer.
Full color to two-color conversion exists for POS (Point Of Sale) ink-jet and thermal printers as described in commonly assigned U.S. Pat. No. 6,206,504, commonly assigned U.S. Pat. No. 6,502,923, commonly assigned U.S. Pat. No. 6,523,937, and commonly assigned co-pending U.S. patent application Ser. No. 09/633,003. In a prior art color conversion process for inkjet printing, the color intensity of a pixel in the full color image is compared to a single threshold and a decision is made to print a dot (pixel) or not to print a dot (pixel) in order to create the two-color image.
The present invention provides an enhanced algorithm for the conversion of a full color image to a two-color image in connection with high quality printing technologies. The present invention is particularly suited to a two color thermal printer having a primary color (e.g., black) and an alternate color (e.g., red).